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Hybrid Micro Grids for rural electrification: Developing Appropriate Technology
TRAMA TECNOAMBIENTAL, S.L.Avda. Meridiana 153
08026 BarcelonaTel: + 34 934 463 234Fax: + 34 934 566 948
Antoine Graillot, TTA
AIE Event
Maputo, June 10th 2009
Relevant aspects in rural electrification
Cost-effectiveness
The needs: demand analysis and segmentation
The technologies and design practice
Ownership and operational scheme
User and operator training/capacity building
Monitoring and performance assessment
Lessons learned in demonstration projects
What is a Hybrid Mini Grid with RE?
A combination of different but complementary energy generation
systems based on renewable energies or mixed (RES- genset)
Hybrid powered mini-grids can provide steady community-level
electricity service, such as village electrification, offering also the
possibility to be upgraded through grid connection in the future
Total installed power up to 100 kW (according to IEC)
Distribution line in Low Voltage (up to 1.000V) (only distribution)
Single or 3-phases
PV Hybrid Mini Grid in West Bank, Palestine
Classification of Hybrid Mini GridsDC coupling
AC/DC Converters
Charge Controllers
DC Loads
AC Loads
=~
Photovoltaics Wind Energy Genset Hydro Power
Battery Inverter
Optional
=~
=~
DC bus
linebar
All electricity generating
components are connected to
a DC bus line from which the
battery is charged.
AC generating components
need an AC/DC converter.
The battery, controlled and
protected from over charge
and discharge by a charge
controller, then supplies power
to the DC loads in response to
the demand.
AC loads can be optionally
supplied by an inverter.
Classification of Hybrid Mini GridsAC coupling
AC bus line 230 or 400 V
DC Loads
AC Loads
Photovoltaics Wind Energy Genset Hydro Power
Battery
Master Inverter
and
Battery charger
Inverters
Optional
AC/DC Converters=~
=~
All electricity generating
components are connected to
an AC bus line.
AC generating
components may be directly
connected to the AC bus line or
may need a AC/AC converter
to enable stable coupling of the
components.
In both options, a bidirectional
master inverter controls the
energy supply for the AC loads
and the battery charging.
DC loads can be optionally
supplied by the battery.
Classification of Hybrid Mini GridsDC and AC coupling
GensetHydro Power
AC Loads
DC Loads
=~
Photovoltaics Wind Energy
Charge Controllers
AC/DC Converter
Master Inverter
and
Battery charger
AC bus line 230 or 400 V
DC bus
linebar
DC and AC electricity
generating components are
connected at both sides of a
master inverter, which controls
the energy supply of the AC
loads.
DC loads can be optionally
supplied by the battery.
On the AC bus line, AC
generating components may
be directly connected to the AC
bus line or may need a AC/AC
converter to enable stable
coupling of the components.
0
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0 0,5 1 1,5 2 2,5 3 3,5
MIL
ES
DE
EU
RO
S
Kilómetros
Red Media Tensión
FV autónoma 2200 Wh/día (3,2 -4,0 HSP)
FV autónoma 3300 Wh/día (3,2 -4,0 HSP)
FV autónoma 6325 Wh/día (3,2-4,0 HSP)
Red Baja Tensión
PV cheaper than grid extension for remote areas
Comparison of investment costs between grid extension and off-grid PV in Spain
PV more sustainable than fossil fuelled Gensets
0,00
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0,50
0,60
0,70
0,80
0,90
1,00
Grupo electrógeno
directo
Grupo electrógeno +
baterías
FV híbrida (25%
fracción solar)
FV híbrida (80%
fracción solar)
FV (100% fracción
solar)
€/k
Wh
0,0
4,0
8,0
12,0
16,0
20,0
€/m
es
us
ua
rio
me
dio
Combustible G&O&M Inversión microrred
Source: http://www.esmap.org/filez/pubs/620200785630_Peru_Solar-Diesel_Amazon_111-07.pdf
Levelized costs for PV and Diesel technologies in microgrid for 340 users in Peru
(D.R. 5%, Diesel: 0,57 €/l)
PV more sustainable than fossil fuelled Gensets
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
Grupo electrógeno
directo
Grupo electrógeno
+ baterías
FV híbrida (25%
fracción solar)
FV híbrida (80%
fracción solar)
FV (100% fracción
solar)
€/k
Wh
0
4
8
12
16
20
€/m
es
us
ua
rio
me
dio
Combustible G&O&M Inversión (microplanta + microrred)
Levelized costs for PV and Diesel technologies in microgrid for 340 users in Peru
(D.R. 5%, Diesel: 1 €/l)
Source: http://www.esmap.org/filez/pubs/620200785630_Peru_Solar-Diesel_Amazon_111-07.pdf
VISION: Universal electrification-individual plants and micro grids under one operational scheme
Individual Micro-Power PlantsMSG
MSG
From individual PV autonomous power plants to microgrids
Application types Types of uses
Home applications LightingAudio/videoRefrigerator(s)Small household appliancesWashing machineIronsFreezer(s)Odd jobs
Public areas applications(places of collective life: worship halls, community centre, healthcentre, etc.)
The same appliances as above areused, but more and more powerful.
Public lighting.
Village water pumping.
Economic activities applications Process equipment supply (mainlymotors)
Individual PV micro plants in Europe
Multi-user microgrids in Developping Countries
Comparison of PV Individual and Micro grids
Advantages Disadvantages
IndividualElectrificationMicro plants
• Consumption is user managed on a day to day basis.
• System black outs affect just one user.
• Systems can be easily moved to a new location.
• Limited surge power capacity.
• Monitoring individual systems can be expensive and difficult.
• Maintenance and repair service complex to organize in rural areas.
Multiuser Solar Grids (MSG)
• Improved quality (surge power, load shedding, etc).
• Lower investment for compact villages.
• Energy saving can be practiced using improved management tools.
• Lower maintenance costs.
• Telemetry can be economic for monitoring system status.
• If the power plant fails, everybody is cut off.
• Social rules required to distribute energy availability.
• Local management required.
• Systems generally need to be serviced on site.
Challenge: sharing the energy available without conflicts
Energy distribution and metering problem!
Energy Availability
General scheme for tariff: users pay for consumed kWh
In stand-alone electrification with RE, Key aspect is the available energy and not the installed power
Tariffs must reflect this idea
Tariff based on the Energy Availability (similar to fee for service ≠ prepayment)
Clearer and easier financial planning and vision
BACKGROUND: Typical Design approach
Technical specification for PV-hybrid micro-power plants (<100 kW, LV) partially adapted from IEC 62257 TS series
Demand analysis and segmentation
Monitoring of systems to validate technology and the service
10 yr. Service horizon with local operator and local capacity building
Standardized technical solutions with high PV penetration
Experience in Design and Project management of PV-hybrid micro-power plants in rural areas of southern Europe, Africa, Latin America, Pacific …
BACKGROUND: Typical Technical Specification
Battery: Pb-tubular, vented, DODmax=75%, A>3 days, 48V
Load Management: user interface, automatic load disconnect
Etc.
Data logging: based on CEI 61724 (JRC guidelines)
PV modules: crystalline CEI 61215 - 2
Inverter: sinusoidal > 85% +25W pilot inverter
PV Charge controller: MPPT
System bus-bar voltage: < 75V DC (SELV)
Load electrical supply: Mainly standard AC quality single phase
DC coupled topology, high fraction of Renewable Energy generation
From single user to villages: MSG (Multi user Solar Grid) up to 150 kW.h/day
Typical layout (DC bus-bar micro power plant+AC single phase grid )
Typical load profilesProfile 1- Daily Cycle rigid slim loads
PROFILE LOAD
AV
OID
AB
LE
DEFER
AB
LE
INTE
RR
UP
T.
MO
DU
LAB
LE
NO NO NO
NO NO YES NO
1100
TYPICAL DAILY
RANGE
(Wh/day)
550 1100
NO
275 275
550 1100
2a
2b
2c
YES NO YES YES 0
A
A
Profile 2- Base Load
2a-Base Load 2b- Base Load Interruptible 2c- Base Load- Stand-by
Profile 3- Daily Deferrable load
Profile 4- Periodical Deferrable load
Profile 5- “ Dump or ballast” load
Typical load profiles
Two key points
The main actor for load management is the user
• Training needed
Load management requires measurement and broadcast of information on system status
• Power and Energy generation
• Power and Energy consumption
• Energy availability
• Battery status
Load management tools
User information interface + training
Automatic total load disconnect
Automatic selective load switching
Individual Energy limitation (multi user system)
User interface
Active display
Remote display
Data logging
RESULTS OF INDIVIDUAL LOAD SENSITIVITY ANALYSIS (careful user: good operator)
SL05028
1000
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1600
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2600
0 1 2 3 4 5 6 7 8Hp
Wh/d
Spring Summer Autum Winter DD (Wh)Spring-06 Summer-06 Autum-06 Winter-07
Electricity Dispenser / meter
Metering and invoicing interface
Energy and power limitation and guidance according to tariff contracted and generation status
User pays for availability of energy, not for the consumed energy
Sharing of energy among users
• Application and control of new
tariff systems (progressive
tariffs, EDA,...)
• Energy limitation according
to tariff contracted
• Low consumption energy
meters
• Incentives for active load
management
• Flexibility in energy use –
sharing of energy between
neighbours
Progressive tariff scheme
0
0,2
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1
17 33 66 134 >134
Consumption blocks (kWh/month)
Ta
riff
va
ria
ble
ch
arg
e (
€/k
Wh
)
Sharing of energy among users
Combination of user questionnaires and data logger
Monitoring
Data logger:built-in device in power conditioner
Hourly Data Storage (1 year):
Average and total hourly values
Parameters:
all relevant energy flows
solar irradiance
information on battery (voltage, SOC, etc.)
others
• User records:
– Satisfaction ??
– Electrolyte level in battery
– Black outs ?
Typical monitoring data
Examples MSG
Akkan, Morocco
Akkan, Morocco
PV HYBRID POWER PLANT
PV GENERATOR
Installed PV capacity 5.760 Wp
Module type 80 Wp 36 cell – mono crystalline
Number of modules 72
Inclination / orientation 43º / +5º S
PV CHARGE CONTROLLER
Rated power 6.000 Wp
Control algorithm MPPT - Boost
BACK UP GENSET
Rated power 8,2 kVA single phase
Fuel Diesel
BATTERY
Number of elements (voltage) 24 (48V)
Model Hawker 2AT1500
Capacity (C100) 1.500 Ah
Autonomy 4 days
INVERTER
Voltage input / output 48 V DC / 230 V AC
Rated power 7.200 W
Harmonic distortion < 2,5%
DATA LOGGER
Memory / log frequency 300 kbyte / hourly
Type of data Energy, voltage, radiation, etc.
ELECTRICITY DISPENSER – METER
Input 230 V AC 50 Hz
Maximum current 10 A
Algorithm Configurable Daily Energy Deliverability
STREET LIGHTING
Number of lamps 13
Type 70 W hp sodium / 2 level electronic ballast
Total power - high 910 W
Total power - low 683 W
INDIVIDUAL LOADS
Households 275 Wh/day 23
Households 550 Wh/day 3
School 550 Wh/day 1
Mosque 550 Wh/day 1
Technology-PV hybrid power plant
San Lorenzo, Ecuador (LA)
Typical household San Lorenzo, Ecuador (LA)
Technology-distribution microgrid
San Lorenzo, Ecuador (LA)
User interface and loads
Diakha Madina, Senegal
Diakha Madina, Senegal
PV ARRAY
PV installed power 3.150 Wp
PV Module model PW750 75 Wp 12V
Nº PV modules 42
Orientation/Inclination 0º S / 10º S
PV Area 46 m2
AVAILABLE ENERGY
Available Energy (Wh/day) 4.803
Irradiation (ḠpHp) 5 HPS
Month of design December
BATTERY
Nº elements 24
Battery type Tudor 6 OPzS 420
Capacity (C100) 672 Ah
Day of autonomy 4 days
CHARGE CONTROLLER
Regulation capacity 4.000 Wp
Mode of charge control MPP Tracker
INVERTER
Input / Output voltage 48 V DC / 230 V AC
Nominal Power 3.600 W
DC/DC Converter (12 V) 10A máxima de corriente
Harmonic distorsion < 2%
DATA LOGGING
Memory / freq. of logging 300 kbyte / hourly
PUBLIC LIGHTING
Number 2
Type of lamp 70 W / electronic ballast
PUMPING SYSTEM
Power of the pump 1.100 W
Flow 5m3/h
Deep 49 m
Height of the tank 7 m
Tank capacity 20 m3
BACK-UP GENSET
Nominal power 4,2 kW single phase
Fuel Diesel
Current situation in SSA
Current situation in SSA
Low population density
Remoteness from the public grid
Low demand in electricity
High energy losses on the transmission lines
High costs of grid extension and connection
High Operation and Maintenance costs
Current situation in SSA
Existing mini grids running with Genset (many are not working)
Many villages and households and villages not connected to the grid
But essential to bring electricity, even basic needs (high value for the first kWh)
Present and future potential
Villages not connected to the grid, where the grid extension is too expensive and not cost effective: micro-grid for basic needs (health, school, water, etc)
Villages with obsolete diesel generator because of the high running costs (Operation and Maintenance): refurbishing distribution grid, electrical installations, etc
Short-term (0-2 years)
Medium-term (5-6 years)
Long-term (10 years onwards)
Villages not connected to the grid: extension of the mini-grid to private applications and productive uses
Villages not connected to the grid: interconnection of several mini-grids between them or/and the national grid
Constraints and limitations
Training and capacity building
High costs of investment
Critical number for maintenance
Management of accumulated money
Social organization may be a critical issue depending of the management model
Unfair regulation (unfair regulations that discriminate against technologies that are especially suited to rural areas)
LESSONS LEARNED in 15 years of practice
User interface is critical !
PV-hybrid micro grids are an acceptable long term option and expanding market
Public subsidies in rural electrification must be technology neutral
Typical average energy consumption is low but very valuable to users
Demand limitation not a problem if EE appliances available
Generation technology more and more reliable and adequate but...• Load management is an important issue• Stand-by loads in appliances dramatically increasing !!
Operator recommended for long term security. Fixed user fees better
